Post on 11-Jan-2016
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The Integument o Is the largest system of the body
• 16% of body weight
• 1.5 to 2 m2 in area
• The integument is made up of two parts
1. Cutaneous membrane (skin)
2. Accessory structures
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Two Components of the Cutaneous Membrane
1. Outer epidermis
• Superficial epithelium (epithelial tissues)
2. Inner dermis
• Connective tissues
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Accessory Structures
o Originate in the dermis
o Extend through the epidermis to skin surface
• Hair
• Nails
• Multicellular exocrine glands
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Connections
o Cardiovascular system
• Blood vessels in the dermis
o Nervous system
• Sensory receptors for pain, touch, and temperature
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Hypodermis (Superficial Fascia or Subcutaneous
Layer)
o Loose connective tissue
o Below the dermis
o Location of hypodermic injections
Cutaneous MembraneAccessory Structures
Epidermis
Dermis
Papillary layer
Reticular layer
Hypodermis
Hair shaft
Pore of sweatgland duct
Tactile corpuscle
Sebaceous gland
Arrector pili muscle
Sweat gland duct
Hair follicle
Lamellated corpuscle
Nerve fibers
Sweat gland
Artery
Vein
Fat
Cutaneousplexus
Cutaneous Membrane
Epidermis
Dermis
Papillary layer
Reticular layer
Hypodermis
Accessory Structures
Hair shaft
Pore of sweatgland duct
Tactile corpuscle
Sebaceous gland
Arrector pili muscle
Sweat gland duct
Hair follicle
Lamellated corpuscle
Nerve fibers
Sweat gland
Artery
Vein
Fat
Cutaneousplexus
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Functions of Skin
o Protection of underlying tissues and organs
o Excretion of salts, water, and organic wastes (glands)
o Maintenance of body temperature (insulation and
evaporation)
o Production of melanin
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Functions of Skin
o Production of keratin
o Synthesis of vitamin D3
o Storage of lipids
o Detection of touch, pressure, pain, and temperature
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The Epidermis
o Is avascular stratified squamous epithelium
• Nutrients and oxygen diffuse from capillaries in the dermis
Thick skin LM 154
Epidermalridge
Dermalpapilla
Stratumlucidum
Stratumcorneum
Basementmembrane
Dermis
Dermis
Epidermis
Epidermalridge
Dermalpapilla
Thin skin LM 154
The structural relationship andinterface between the epidermisand underlying dermis. Theproportions of the various layersdiffer with the location sampled.
Dermis
Epidermis
Epidermalridge
Dermalpapilla
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Cells of the Epidermis
o Keratinocytes
• Contain large amounts of keratin
• Are the most abundant cells in the epidermis
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Thin Skin
o Covers most of the body
o Has four layers of keratinocytes
Thick Skin
o Covers the palms of the hands and soles of the feet
o Has five layers of keratinocytes
A micrograph ofthin skin, which covers most ofthe exposedbody surface.
Stratumcorneum
Basementmembrane
Dermis
Thin skin LM 154
A micrograph of thickskin, which coversthe surface of thepalms and the solesof the feet.
Thick skin LM 154
Epidermalridge
Dermalpapilla
Stratumlucidum
Stratumcorneum
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Structures of the Epidermiso The five strata of keratinocytes in thick skin
o From basal lamina to free surface
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum
Thick skin LM 210
Surface
Stratumcorneum
Stratumlucidum
Stratumgranulosum
Stratumspinosum
Stratum basale
Basementmembrane
DermisPapillary layer of dermis
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Stratum Basaleo Is attached to basement membrane by
hemidesmosomes
o Forms a strong bond between epidermis and dermis
o Forms epidermal ridges (e.g., fingerprints)
o Dermal papillae (tiny mounds)
• Increase the area of basement membrane
• Strengthen attachment between epidermis and dermis
o Has many basal cells or germinative cells
Thick skin SEM 25
Epidermalridge
Pores of sweatgland ducts
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Specialized Cells of Stratum Basale
o Merkel cells
• Found in hairless skin
• Respond to touch (trigger nervous system)
o Melanocytes
• Contain the pigment melanin
• Scattered throughout stratum basale
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Stratum Spinosum — the “spiny layer”
o Produced by division of stratum basale
o Eight to ten layers of keratinocytes bound by
desmosomes
o Cells shrink until cytoskeletons stick out (spiny)
o Continue to divide, increasing thickness of epithelium
o Contain dendritic (Langerhans) cells, active in immune
response
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Stratum Granulosum — the “grainy layer”
o Stops dividing, starts producing
• Keratin • A tough, fibrous protein
• Makes up hair and nails
• Keratohyalin • Dense granules
• Cross-link keratin fibers
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Cells of Stratum Granulosum
o Produce protein fibers
o Dehydrate and die
o Create tightly interlocked layer of keratin surrounded by
keratohyalin
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Stratum Lucidum — the “clear layer”• Found only in thick skin
• Covers stratum granulosum
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Stratum Corneum — the “horn layer”• Exposed surface of skin
• 15 to 30 layers of keratinized cells (more in the thickest
skin)
• Water resistant
• Shed and replaced every 2 weeks
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Keratinization o The formation of a layer of dead, protective cells filled
with keratin
o Occurs on all exposed skin surfaces except eyes
o Skin life cycle
o It takes 15–30 days for a cell to move from stratum basale to stratum corneum
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Perspirationo Insensible perspiration
• Interstitial fluid lost by evaporation through the stratum corneum
o Sensible perspiration • Water excreted by sweat glands
• Dehydration results:• From damage to stratum corneum (e.g., burns and blisters
[insensible perspiration])• From immersion in hypertonic solution (e.g., seawater
[osmosis])
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Hydration
o Results from immersion in hypotonic solution (e.g.,
freshwater [osmosis])
o Causes swelling of epithelial cells and expansion of the
skin to accommodate the extra water, which appears as
wrinkly skin
o No one knows why the skin wrinkles
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Skin Color is Influenced by Two Pigments
1. Carotene
2. Melanin
o Blood circulation (red blood cells)
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Caroteneo Orange-yellow pigment
o Found in orange vegetables
o Accumulates in epidermal cells and fatty tissues of the
dermis
o Can be converted to vitamin A
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Melanino Yellow-brown or black pigment
o Produced by melanocytes in stratum basale
o Stored in transport vesicles (melanosomes)
o Transferred to keratinocytes
Melanocytes LM 600
Melanocytes in stratum basale
Melaninpigment
Basementmembrane
Basementmembrane
Melanosome
Keratinocyte
Melanin pigment
Melanocyte
Melanoma
Basal cell carcinoma
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Function of Melanocytes
o Melanin protects skin from sun damage
o Ultraviolet (UV) radiation
• Causes DNA mutations and burns that lead to cancer and
wrinkles
o Skin color depends on melanin production, not number of
melanocytes
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Capillaries and Skin Coloro Oxygenated red blood contributes to skin color
• Blood vessels dilate from heat, skin reddens
• Blood flow decreases, skin pales
o Cyanosis• Bluish skin tint
• Caused by severe reduction in blood flow or oxygenation
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Illness and Skin Coloro Jaundice
• Buildup of bile produced by liver
• Yellow color
o Pituitary tumor• Excess MSH (melanocyte stimulating hormone)
o Addison’s disease• A disease of the pituitary gland
• Skin darkening
o Vitiligo• Loss of melanocytes
• Loss of color
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Vitamin D3
o Epidermal cells produce cholecalciferol (vitamin D3)
• In the presence of UV radiation
o Liver and kidneys convert vitamin D3 into calcitriol
• Aids absorption of calcium and phosphorus
o Insufficient vitamin D3
• Can cause rickets and depressed immune system
• Has been shown as a potential treatment for MS (in
conjuction with traditional treatments)
• Low levels appear in those with some cancers
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Epidermal Growth Factor (EGF) o Powerful growth factor
o Produced by glands (salivary and duodenum)
o Used in laboratories to grow skin grafts
Functions of EGFo Promotes division of germinative cells
o Accelerates keratin production
o Stimulates epidermal repair
o Stimulates glandular secretion
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The Dermiso Located between epidermis and subcutaneous layer
o Anchors epidermal accessory structures (hair follicles, sweat glands)
o Two components
1. Outer papillary layer
2. Deep reticular layer
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The Papillary Layero Consists of areolar tissue
o Contains smaller capillaries, lymphatics, and sensory
neurons
o Has dermal papillae projecting between epidermal
ridges
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The Reticular Layero Consists of dense irregular connective tissue
o Contains larger blood vessels, lymphatic vessels, and
nerve fibers
o Contains collagen and elastic fibers
o Contains connective tissue proper
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Dermatitiso An inflammation of the papillary layer
o Caused by infection, radiation, mechanical irritation, or
chemicals (e.g., poison ivy)
o Characterized by itch or pain, redness, and/or flaky skin
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Dermal Strength and Elasticityo Presence of two types of fibers
1. Collagen fibers• Very strong, resist stretching but bend easily• Provide flexibility
2. Elastic fibers• Permit stretching and then recoil to original
length• Limit the flexibility of collagen fibers to prevent
damage to tissue• Skin turgor
• Properties of flexibility and resilience
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Skin Damageo Sagging and wrinkles (reduced skin elasticity) are
caused by:
• Dehydration
• Age
• Hormonal changes
• UV exposure
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Skin Damageo Stretch marks
• Thickened tissue resulting from excessive stretching
of skin due to:
• Pregnancy
• Weight gain
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Cleavage Lineso Collagen and elastic fibers in the dermis
• Arranged in parallel bundles
• Resist force in a specific direction
o Cleavage (tension) lines establish important patterns• A parallel cut remains shut, heals well
• A cut across (right angle) pulls open and scars
ANTERIOR POSTERIOR
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The Dermal Blood Supplyo Cutaneous plexus
• A network of arteries along the reticular layer
o Papillary plexus • Capillary network from small arteries in papillary layer
o Venous plexus• Capillary return deep to the papillary plexus
o Contusion• Damage to blood vessels resulting in “black-and-blue”
bruising
Hair
Papillarylayer
Reticularlayer
Cutaneousplexus
Papillaryplexus
Epidermalridges
Dermalpapillae
Capillary loopof papillary
plexus
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Innervation of the Skin
o Nerve fibers in skin control:
• Blood flow
• Gland secretions
• Sensory receptors • Light touch—tactile corpuscles, located in dermal papillae• Deep pressure and vibration—lamellated corpuscles, in the
reticular layer
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The Hypodermis (Subcutaneous Layer)o Lies below the integument
o Stabilizes the skin
o Allows separate movement
o Made of elastic areolar and adipose tissues
o Connected to the reticular layer of integument by connective tissue fibers
o Few capillaries and no vital organs
o The site of subcutaneous injections using hypodermic needles
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Deposits of Subcutaneous Fato Distribution patterns determined by hormones
o Reduced by cosmetic liposuction (lipoplasty)
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Hair, Hair Follicles, Sebaceous Glands,
Sweat Glands, and Nailso Integumentary accessory structures
o Derived from embryonic epidermis
o Located in dermis
o Project through the skin surface
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Human Bodyo The human body is covered with hair, except:
• Palms
• Soles
• Lips
• Portions of external genitalia
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Functions of Hairo Protects and insulates
o Guards openings against particles and insects
o Is sensitive to very light touch
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The Hair Follicleo Located deep in dermis
o Produces nonliving hairs
o Wrapped in a dense connective tissue sheath
o Base is surrounded by sensory nerves (root hair
plexus)
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Accessory Structures of Hairo Arrector pili
• Involuntary smooth muscle
• Causes hairs to stand up
• Produces “goose bumps”o Sebaceous glands
• Lubricate the hair
• Control bacteria
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Regions of the Hair
o Hair root
• Lower part of the hair
• Attached to the integument
o Hair shaft
• Upper part of the hair
• Not attached to the integument
Single hair follicle, showingthe associated accessorystructures; a superficialview of the deeper portionsof the follicle illustrates theconnective tissue sheathand the root hair plexus.
Exposedshaftof hair
Sebaceousgland
Arrectorpilimuscle
Connectivetissue sheath
Root hairplexus
Cross section through ahair follicle and a hair, nearthe junction between thehair root and hair shaft.
Connective tissue sheath
Hair Structure
Follicle Structure
The medulla, or
core, of the hair
contains a flexible
soft keratin.
The cortex contains thick
layers of hard keratin,
which give the hair its stiff-
ness.
The cuticle, although
thin, is very tough, and
it contains hard keratin.
The internal root sheath surroundsthe hair root and the deeper portion ofthe shaft. The cells of this sheathdisintegrate quickly, and this layer doesnot extend the entire length of the hairfollicle.
The external root sheath extendsfrom the skin surface to the hair matrix.
The glassy membrane is a thickened,clear layer wrapped in the denseconnective tissue sheath of the follicleas a whole.
Diagrammatic sectionalview along the long axisof a hair follicle.
Boundary betweenhair shaftandhair root
Hair shaft
Sebaceousgland
Arrectorpili muscle
Hair root
Connectivetissue sheath
Hair bulb
Hair matrix
Hair papilla
Longitudinal section through twohair follicles, showing the base ofthe follicle and the matrix andpapilla at the root of the hair.
Sebaceous gland
Hair shaft
Hair
Glassy membrane
Subcutaneous adiposetissue
Connective tissue sheathof hair
Cortex
Medulla
Hair matrixPapillaHair bulb
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Hair Production
o Begins at the base of a hair follicle, deep in the dermis
• The hair papilla contains capillaries and nerves
• The hair bulb produces hair matrix
• A layer of dividing basal cells
• Produces hair structure
• Pushes hair up and out of skin
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Hair Shaft Structure
o Medulla
• The central core
o Cortex
• The middle layer
o Cuticle
• The surface layer
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Keratino As hair is produced, it is keratinized
• Medulla contains flexible soft keratin
• Cortex and cuticle contain stiff hard keratin
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Hair Growth Cycleo Growing hair
• Is firmly attached to matrix
• Club hair
• Is not growing because it is in its final
stage of growth
• Is attached to an inactive follicle
• Once the club hair is gone, no more hair
will emerge from that follicle
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Hair Growth Cycleo New hair growth cycle
• Follicle becomes active
• Produces new hair
• Club hair is shed
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Types of Hairs
o Vellus hairs
• Soft, fine
• Cover body surface
o Terminal hairs
• Heavy, pigmented
• Head, eyebrows, and eyelashes
• Other parts of body after puberty
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Hair Color
o Produced by melanocytes at the hair papilla
o Determined by genes
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Exocrine Glands in Skino Sebaceous Glands (oil glands)
• Holocrine glands
• Secrete sebum
o Two Types of Sweat Glands
1. Apocrine glands
2. Merocrine (eccrine) glands
• Watery secretions
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Types of Sebaceous (Oil) Glandso Simple branched alveolar glands
• Associated with hair follicles
o Sebaceous follicles
• Discharge directly onto skin surface
• Sebum
• Contains lipids and other ingredients
• Lubricates and protects the epidermis
• Inhibits bacteria
Epidermis
Dermis
Subcutaneouslayer
Sebaceous follicle Sebaceous gland
Sebaceous gland LM 150
Basal cells
Mitosis and growth
Breakdown ofcell membranes
Lumen
Discharge ofsebum
Basementmembrane
Lumen(hair removed)
Wall of hair follicle
Epidermis
Dermis
Subcutaneouslayer
Sebaceous follicle Sebaceous gland
Basal cells
Mitosis and growth
Breakdown ofcell membranes
Lumen
Discharge ofsebum
Basementmembrane
Lumen(hair removed)
Wall of hair follicle
Basal cells
Basementmembrane
Lumen(hair removed)
Wall of hair follicle
Sebaceous gland LM 150
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Apocrine Sweat Glands
o Found in armpits, around nipples, and groin
o Secrete products into hair follicles
o Produce sticky, cloudy secretions
o Break down and cause odors
o Surrounded by myoepithelial cells
• Squeeze apocrine gland secretions onto skin surface
• In response to hormonal or nervous signal
Apocrine sweat glandssecrete a thick, odorousfluid into hair follicles.
LM 459Apocrine sweat gland
Lumen
Myoepithelial cell
Connectivetissue of dermis
Apocrinegland cells
Duct ofapocrine
sweat gland
Sectional planethrough apocrine
sweat gland
A sectionthrough a merocrinesweat gland
Sweat pore
Duct
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Merocrine (Eccrine) Sweat Glands o Widely distributed on body surfaceo Especially on palms and soleso Coiled, tubular glandso Discharge directly onto skin surfaceo Sensible perspirationo Water, salts, and organic compoundso Functions of merocrine sweat gland activity
• Cools skin• Excretes water and electrolytes• Flushes microorganisms and harmful chemicals from
skin
Duct ofapocrine
sweat gland
Sectional planethrough apocrine
sweat gland
A sectionthrough a merocrinesweat gland
Sweat pore
Duct
Merocrine sweat glandsdischarge a watery fluidonto the surface of theskin.
LM 243Merocrinesweat gland
Lumen
Myoepithelialcells
Merocrinegland cells
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Other Integumentary Glands
1. Mammary glands
• Produce milk
2. Ceruminous glands
• Produce cerumen (earwax)
• Protect the eardrum
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Control of Glandso Autonomic nervous system (ANS)
• Controls sebaceous and apocrine sweat glands• Works simultaneously over entire body
o Merocrine sweat glands• Controlled independently• Sweating occurs locally
o Thermoregulation• The main function of sensible perspiration• Works with cardiovascular system• Regulates body temperature
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Nails
o Protect fingers and toes
o Made of dead cells packed with keratin
o Metabolic disorders can change nail structure
Nail Production
o Occurs in a deep epidermal fold near the bone called the
nail root
A longitudinal section
A superficial view
A cross-sectional viewEponychium
Proximalnail fold
Lunula
Nail body
Lateral nail fold
Free edge
Directionof growth
Nailbody
Lateralnail
groove
Nailbed
Phalanx(bone of
fingertip)
Eponychium
Proximal nail fold
Nail root
Lunula Nail body
Epidermis Dermis Phalanx Hyponychium
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Repair of the Integument Following an Injuryo Bleeding occurs
o Mast cells trigger inflammatory response
o A scab stabilizes and protects the area
o Germinative cells migrate around the wound
o Macrophages clean the area
o Fibroblasts and endothelial cells move in, producing
granulation tissue
Bleeding occurs at the siteof injury immediately afterthe injury, and mast cellsin the region trigger aninflammatory response.
Epidermis
Dermis
Mast cells
After several hours, ascab has formed and cellsof the stratum basale aremigrating along the edges of the wound. Phagocyticcells are removing debris,and more of these cellsare arriving via theenhanced circulation inthe area. Clotting aroundthe edges of the affectedarea partially isolates theregion.
Migratingepithelialcells
Macrophagesand fibroblasts
Granulationtissue
Fibroblasts
One week after the injury,the scab has beenundermined by epidermalcells migrating over themeshwork produced byfibroblast activity.Phagocytic activityaround the site hasalmost ended, and thefibrin clot is breaking up.
Scartissue
After several weeks, thescab has been shed, andthe epidermis is complete.A shallow depressionmarks the injury site, butfibroblasts in the dermiscontinue to create scartissue that will graduallyelevate the overlyingepidermis.
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Repair of the Integument Following an Injury
o Fibroblasts produce scar tissue
• Inflammation decreases, clot disintegrates
• Fibroblasts strengthen scar tissue
• A raised keloid may form, which is an overgrowth of
collagen during the healing process
Head 9%
Upper limb9% each
Trunk 36%(front and back)
Genitalia 1%
Lower limb18% each
Head 15%
Trunk 32%(front and back)
Lower limb17% each
Upper limb 9% each
Genitalia 1%
ADULT CHILD (5-year-old)
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Effects of Aging
o Epidermal thinning
o Decreased numbers of dendritic (Langerhans) cells
o Decreased vitamin D3 production
o Decreased melanocyte activity
o Decreased glandular activity (sweat and oil glands)
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Effects of Aging
o Reduced blood supply
o Decreased function of hair follicles
o Reduction of elastic fibers
o Decreased hormone levels
o Slower repair rate
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Importance of the Integumentary System
o Protects and interacts with all organ systems
o Changes in skin appearance are used to diagnose
disorders in other systems